1. Field
The present invention generally relates to an image forming method and/or apparatus. More particularly, it may relate to an image forming method and/or apparatus capable of accurately detecting pattern images formed on a detection target such as image carriers or an intermediate transfer body, or a transfer-material carrier, for example.
2. Discussion of the Background
Background electrophotographic image forming apparatuses such as copiers, printers, facsimiles, and the like create a toner image on a surface of an image carrier (i.e., a photoconductor) or an intermediate transfer body. These apparatuses generally form a toner pattern image for test and detect a density of the toner pattern image typically by using an optical detecting apparatus having a photodetector. Based on a result of the detection, the apparatuses adjust the density so as to obtain a stable image density.
The optical detecting apparatus generally includes a reflection-type photodetector that has a light-emitting element and a light-receiving element. To detect the toner pattern image, the optical detecting apparatus emits light from the light-emitting element onto a toner pattern image and detects, with the light-receiving element, the light reflected from the toner pattern image.
A variety of reflection-type photodetectors have been proposed for such a purpose. One example reflection-type photodetector includes a number of components such as a light-emitting element, an oscillator, a drive circuit, a light receiving part, a processing circuit and so on, which are mounted on a single circuit board, serving as one module.
In general, the above-described background image forming apparatuses have been subjected to crucial requirements of downsizing. To reduce a size of the image forming apparatus, almost every space available inside the image forming apparatus may be used to enclose as many parts as possible. This results in a growing number of restrictions on space in which to arrange the photoreceptors; therefore an arrangement of the reflection-type photodetectors has become more difficult.
Some image forming apparatuses use an optical detecting apparatus having a plurality of photodetectors to detect a toner pattern image formed particularly on an intermediate transfer belt so as to improve detection accuracy and reduce detecting time. However, as the number of photodetectors are increased, the dimension of the optical detecting apparatus including an operating circuit for photodetectors becomes larger than a conventional single photodetector. Consequently, the optical detecting apparatus cannot be arranged at a position considered as optimum for control.
When a printed circuit board is provided with a plurality of photodetectors, a corresponding number of operating circuits for the plurality of photodetectors also need to be provided. In this case, however, a number of physical and spatial restrictions may be enforced on an installation of the optical detecting apparatus to the image forming apparatus. For example, it may be difficult to find space for screw holes in a surface of the print circuit board for securing the optical detecting apparatus to the image forming apparatus.
It may also be difficult to reserve space on the printed circuit board for circuit constituent parts such as connecting parts for inputting and outputting signals. With a relatively small number of photodetectors, all the circuit constituent parts can be arranged on the printed circuit board. However, when a relatively large number of photodetectors are required, arranging the circuit constituent parts on the print circuit board may inevitably fail, resulting in a redesign to enlarge the dimension of the print circuit board.
In addition, when a relatively large number of photodetectors are installed in the optical detecting apparatus, as described above, the constituent parts may intervene as an obstruction to an optical path of the photodetectors. Also, with a relatively large number of photodetectors installed, wiring patterns for the circuits of the photodetectors become complicated, so that such complication on the printed circuit board may cause crosstalk among the wiring patterns.